The problem is caused by a conflict between 2 packages. biblatex-mla works well with biblatex 1.0, and my current version of biblatex is 1.7.

Right now, I know that I need to use tlmgr to remove biblatex 1.7.
My question is related with all the dependencies. According to the package manager I need to remove the whole collection of bibtexextra in order to remove biblatex. And I don't know what to do next:

Can I remove the package with (--no-depends) and then install manually biblatex 1.0? or

As you ask what is the best way to resolve the issue: Going back to a very old version can be a temporary workaround only. A real solution would be to file a bug report (in biblatex-mla, I guess), help in finding/removing the bug and then update to the newest version of both biblatex and biber. Of course, this may take some time, maybe a week or two.
–
matthFeb 25 '12 at 11:32

@matth Good advice, but "a week or two" might be a little optimistic in some cases. Apparently biblatex 2.0 will use biber as the sole backend. So this question will likely be useful for bibtex diehards down the road.
–
AudreyFeb 25 '12 at 14:31

With biblatex 1.0, you'll want biber 0.6.5. You have to build biber from the source code as binaries appear to be available only for recent releases. Details can be found in the readme file. To install, just put the resulting biber binary into a folder where your system finds executable files. (La)TeX binaries are typically stored in a subfolder of $TEXMFROOT/bin.

I took advantage of TeX Live Manager (tlmgr). I opened a terminal, I log in as administrator with (su) [I am working with Linux] and then I went to /usr/local

Then I write this command: tlmgr --gui

At this point I was into a graphical version of tlmgr. The repository load by default is pointing the last version [TeX Live 2011], but it is possible to change this repository. Go to the tab tlmgr and select: load other repository.